468 On the AUotropic States of Oxygen ; and on Nitrification. 



and pouring over it acidulated starch-paste containing iodide of 

 potassium, you will perceive the effect produced. The fact which 

 I have ascertained, that the purest water mixed with a little che- 

 mically pure sulphuric acid or potash and kept for some time 

 evaporating in the open air at a temperature of 50° or 60° C. 

 (the loss of the liquid being now and then restored) contains, in 

 the first case, a perceptible quantity of ammonia, and, in the 

 second case, of nitrous acid, may now be easily accounted for. 

 You know that about eighteen months ago I found that, during 

 the slow combustion of phosphorus in moist atmospheric air, 

 very perceptible quantities of nitrite of ammonia are formed, and 

 drew from that fact the inference that the salt is engendered by 

 3 equivalents of water combining directly with 2 equivalents of 

 nitrogen. Now there is to me hardly any doubt that the pro- 

 duction of that nitrite is due to the evaporation of water taking 

 place about the phosphorus, whose temperature, in consequence 

 of its burning state, proves to be higher than that of the sur- 

 rounding medium, and the fact alluded to must therefore be 

 considered only as a particular case of a general rule. The 

 same remark applies to the formation of nitrite of ammonia 

 which takes place during the rapid combustion of charcoal, &c. 

 in atmospheric air. Combustion, as such, has, I believe, nothing 

 to do with that formation. I must not omit to tell you that by 

 means of a large copper still, properly heated, and taking care 

 not to introduce too much water into the vessel at once, I can 

 prepare in a very short time several pints of water with which the 

 reactions of nitrite of ammonia may be produced in the most 

 striking manner. I hope before long to have an opportunity of 

 sending you some of this water. 



I cannot finish my letter without saying a word or two about 

 nitrification in general, a fact hitherto so much enveloped in 

 obscurity. I think the matter is now clear enough. The evapo- 

 ration of water is continually going on in the atmosphere, and 

 along with it the generation of nitrite of ammonia. Now, this 

 salt being put in contact with the alkaline bases or their carbo- 

 nates, nitrites of potash and the other alkalies are formed, which 

 afterwards become gradually oxidized into nitrates. In our rainy 

 countries these salts are w r ashed away almost as soon as formed, 

 and carried into the springs, rivers, &c. ; and there is therefore 

 no accumulation of them as in the East Indies, &c. 



That the formation of our nitrite out of water and nitrogen is 

 a fact highly important for vegetation need hardly be stated. 

 Indeed each plant, by continually evaporating water into the 

 atmosphere, becomes a generator of nitrite of ammonia, prepa- 

 ring, if not all, at least part of its nitrogenous food, and the same 

 thing takes place in the ground on which it stands. I am there- 



